Glushkov was close friends with the late oligarch Boris Berezovsky.
Photograph: Pavel Smertin/AP

Police have launched a murder investigation into the death of the Russian businessman Nikolai Glushkov after a pathologist concluded he died from compression to the neck, suggesting he may have been strangled by hand or ligature.

The Metropolitan police’s counter-terrorism command is retaining its lead role in the investigation “because of the associations Mr Glushkov is believed to have had” but has cautioned that there was no suggestion of a link with the attempted murders of the Russian former spy Sergei Skripal and his daughter, Yulia, in Salisbury almost two weeks ago.

The political row between Britain and Russia was mounting after the Russian foreign ministry said it was summoning the UK ambassador, Laurie Bristow, for a meeting on Saturday, Russian news agencies reported.

At the time of his death, Glushkov was about to defend a claim against him by the Russian airline Aeroflot at the commercial court in London, where he was accused of fraud.

In 2017, during a trial in absentia in Russia, he was sentenced to eight years in prison for stealing $123m from the airline, which then pursued the case in London. Glushkov failed to show up at court in central London on Monday and his body was discovered in south-west London that evening.

The Met said: “Detectives are retaining an open mind and are appealing for any information that will assist the investigation.” Officers want to hear from anyone who may have seen or heard anything suspicious at or near his home in Clarence Avenue in New Malden between Sunday 11 March and Monday 12 March

The police’s belief that Glushkov was killed will increase scrutiny over the safety of Russians in the UK and is likely to stoke tensions in an escalating diplomatic dispute over whether the Kremlin played a role in the Skripal attack, which involved the nerve agent novichok.

On Friday, the foreign secretary, Boris Johnson, blamed the Russian president, Vladimir Putin, for the attack, telling an audience at the Battle of Britain museum in Uxbridge: “We think it overwhelmingly likely that it was his [Putin’s] decision to direct the use of a nerve agent on the streets of the UK, on the streets of Europe, for the first time since the second world war.”

Putin’s spokesman, Dimitry Peskov, denounced the comment as “a shocking and unforgivable breach of diplomatic rules of decent behaviour”. The two nations have already announced tit-for-tat expulsions of diplomats, including 23 embassy staff in London.

At a meeting of European foreign ministers on Monday. Johnson is expected to urge allies to clamp down on Russian espionage and money laundering, but will not table a barrage of new EU-wide economic measures against Russia.

The German chancellor, Angela Merkel, played down the possibility of her country boycotting the football World Cup in Russia in June, saying: “Right now it’s important that there’s an investigation.”

A Russian chemist who worked for 30 years inside the secret military installation where novichok was developed told the Guardian it was impossible that a non-state actor could have been behind the poisoning.

Vil Mirzayanov, 83, said the agent was too dangerous for anyone but a “high-level senior scientist” to handle and he did not see how a criminal organisation or other non-state group could pull off such an attack. “It’s very, very tough stuff,” he said from exile in New Jersey. “I don’t believe it.”

The Organisation for the Prohibition of Chemical Weapons (OPCW) is now formally involved in the process of investigating the nerve agent that has left the Skripals fighting for their lives and a police officer, Nick Bailey, seriously ill in a Salisbury hospital.

Downing Street confirmed that a team of scientists from the OPCW would come to the UK early next week. The process is to be agreed between the OPCW scientists and the lab at Porton Down which originally identified the agent.

Under article 8 of the chemical weapons convention, the OPCW team is expected to take its own samples. That could be either environmental evidence from the Skripal home, their car, or possibly the pub or restaurant that the pair visited, or biomedical samples from the Skripals themselves. Earlier, the OPCW said Russia had not declared information about the existence of the novichok group of nerve agents possibly because stockpiles were thought to have been destroyed in a post-Soviet clampdown on old chemical weapons.

“There is no record of the novichok group of nerve agents having been declared by a state party,” the OPCW said.

In a sign that the Glushkov case is also becoming politicised, Russia’s Investigative Committee announced on Friday that it had opened a murder investigation into the death.

In a statement released just hours before the Scotland Yard announcement, the committee, which handles high-profile cases, said it would manage the investigation “in accordance with the requirements of Russian law”. It said investigators were ready to cooperate with British law enforcement.

The Met stressed that “at this stage there is nothing to suggest any link to the attempted murders in Salisbury, nor any evidence that [Glushkov] was poisoned”.

Police were called by the London ambulance service at 10.46pm on Monday after the 68-year-old was found dead at his home in New Malden. A special postmortem began on Thursday.

In the 1990s Glushkov was a director of the state airline and of Boris Berezovsky’s LogoVaz car company. In 1999, as Berezovsky fell out with Putin and fled to the UK, Glushkov was charged with money laundering and fraud. He spent five years in jail and was freed in 2004. Fearing further arrest, he fled to the UK and was granted political asylum.

In 2011, he gave evidence in a court case brought by Berezovsky against his fellow oligarch Roman Abramovich, who remained on good terms with the Kremlin. Glushkov told the court he had effectively been taken hostage by Putin’s administration, which wanted to put pressure on Berezovsky to sell his stake in the TV station ORT.

In March 2013, Berezovsky was found dead at his ex-wife’s home in Berkshire. Police said they believed he had killed himself but a coroner recorded an open verdict.

The former world chess champion and Russian opposition leader Garry Kasparov said he was “not surprised” Glushkov was murdered.

“I think this is a message addressed to Russians with significant interests abroad who are thinking of cooperating with Robert Mueller [the special counsel investigating alleged collusion with the Trump administration]. It’s a preemptive strike. Tragically it’s not even about Glushkov. They pick someone who is expendable and recognisable,” he said.

Speaking to the Guardian in 2013, Glushkov said he did not believe Berezovsky took his own life. “I’m definite Boris was killed. I have quite different information from what is being published in the media,” he said.

He noted that a large number of Russian exiles, including Berezovsky and Alexander Litvinenko, had died under mysterious circumstances. “Boris was strangled. Either he did it himself or with the help of someone. [But] I don’t believe it was suicide,” Glushkov said. “Too many deaths [of Russian émigrés] have been happening.”